Applications In Plant Breeding Research Articles

Molecular Genetic Approaches to the Study of Phytopathogenic Fungi

Abstract The broad application of chemical crop protectants and intensive plant breeding for the development of agriculture and the management of plant disease have created conditions of environ­ mental concern. Molecular genetic m ethods are being applied to the analysis of phytopathogenic fungi and their corresponding diseases. Rapid development of this research field will permit the isolation and characterization of genes involved in pathogenic processes. A detailed understanding of the molecular events of disease onset and progression will facilitate the design of improved procedures for disease prevention and control. Invited Trends Article

The Use of Coleoptile Responses to Water Stress to Differentiate Wheat Genotypes for Osmoregulation, Growth and Yield

Differences in osmoregulation between genotypes of wheat (Triticum aestivum L.) were identified by measuring responses of coleoptiles to water stress. Seeds were germinated in Petri dishes on germination pads. Water stress was applied when coleoptiles were 1 cm long by either adding polyethylene glycol 6000 (20% w/w) or by removing the lids of the dishes and allowing the pads to dry by evaporation for a period of 2 d, or from the beginning of germination by varying the amount of water in the germination pads. Measurements of the water and osmotic potentials of shoots and roots (using thermocouple psychrometers) were used to estimate turgor pressures. Wheat genotypes showed the same segregation for shoot and root lengths and turgor pressures as they had done in previous studies for flag-leaf osmoregulation and yield. It was concluded that observations of the responses of coleoptile length to water stress could be used in plant-breeding applications to identify differences in osmoregulation between genotypes of wheat.

Direct Genetic Transfers from Aegilops squarrosa L. to Hexaploid Wheat1

Methodology of direct genetic transfer from diploid Aegilops squarrosa L. (2n = 14) to cultivated wheat (Triticum aestivum L.) (2n = 42) was explored as a possible applied plant breeding technique for rapid introgression of useful traits. One or more plants of 31 accessions of A. squarrosa (selected for resistance to certain pests of cultivated wheat) were crossed with ‘Wichita’ or ‘Newton’. A total of 219 hybrid embryos were cultured on a synthetic medium to overcome interploidy hybrid embryo‐endosperm incompatibility. Of the 219 embryos, 114 from crosses involving 17 accessions did not grow and were lost. However, one or more hybrids were obtained from crosses involving the 14 other accessions, and 24 F, hybrids were grown to maturity. The F,s were male sterile, but backcross (BC) progenies included fully fertile and meiotically stable 42‐chromosome plants. The partially fertile BC1 plants had a chromosome number range of 40 to 50; 50% with 2n = 40 to 42 and another 50% with 2n = 49 to 50; the latter arose from the functioning of restitution gametes. The probability of transfer of A. squarrosa genes from an F1hybrid to a single BC1 plant is 0.75. The BC1 and BC2 progenies segregated for several phenotypic traits and several lines with resistance to Hessian fly (Mayetiola destructor Say) biotype D, greenbug (Schizaphis graminum Rond.) biotype E, and leaf rust (Puccinia recondita Rob. ex Desm. f. sp. tritici) culture PRTUS6 were selected. Thus, the use of the embryo rescue method facilitated direct genetic transfers from A. squarrosa to hexaploid wheat, and thereby averted the need of using bridging species or prior synthesis of T. turgidum/A. squarrosa amphiploids to overcome interspecific cross‐incompatibilities.

Restriction fragment polymorphisms as probes for plant diversity and their development as tools for applied plant breeding

Maize and tomato cDNA clones have been hybridized in Southern blotting experiments to plant genomic DNA prepared from different lines to detect restriction fragment polymorphisms (RFPs). In maize we have found that a high degree of genetic variability is present, even among domestic inbred lines. Most randomly chosen maize cDNA clones can be used to detect elements of this variability. Similar levels of polymorphism are observed when genomic DNA is digested with any of a number of different restriction enzymes and probed with individual clones. When a clone is hybridized to genomic DNAs prepared from several different maize lines, a number of different alleles are often detected at a single locus. At the same time one clone can often detect more than one independently segregating locus by cross hybridization to related sequences at other loci. As expected these markers are inherited as simple codominant Mendelian alleles from one generation to the next and colinkage of these markers can be demonstrated in the progeny from a heterozygous parent. In similar studies with tomato, remarkably different results were found. Few RFPs were demonstrable among domestic Lycopersicon esculentum lines although a higher level of variability could be detected when comparing esculentum with its wild Lycopersicon relatives. These results are discussed in relation to the applied uses of RFPs in plant breeding as well as the inherent variability of different plant genomes.

Rating cultivars and trials in applied plant breeding

The number of means ‘m’, from which a particular cultivar differs significantly, is used to arrange cultivars in order of descending superiority. For n cultivars under study, the maximum ‘m’ value corresponding to the best cultivar is n-1, indicating that it exceeds significantly the n-1 other cultivars, and the minimum zero. Because ‘m’ represents an objective and reliable statistical measure of cultivar performance, it has been used to calculate two indexes: (1) performance index, P=100 m/(n-1), giving the percentage of means which a particular cultivar exceeds significantly, and (2) differentiation index, D=200 Σm/n (n-1), giving the percentage of paired comparisons between cultivars that show significant differences. Rating cultivars according to P across years (Py), sites (Ps), and years plus sites (Pys), gives an overall picture of the relative superiority of the entries. Rating trials according to D allows comparisons between trials and offers the possibility when the same sets of entries are compared each year across sites, to identify sites that give maximum differentiation.

The culture of isolated leaf cells and protoplats of higher plants and some applications in genetics, biochemistry and plant breeding

The culture of isolated leaf cells and protoplats of higher plants and some applications in genetics, biochemistry and plant breeding

New approach to pollen culture

RESEARCH on pollen and anther culture is important for genetic and mutation studies, and has many potential applications in plant breeding and crop improvement. In our experience, the technique of pollen culture developed by Nitsch and co-workers1,2, though successful with a wide range of species3, is much more difficult than anther culture and involves procedures which are unreliable and inefficient. Furthermore, plant yields are generally lower than when anther culture is used. We describe here an alternative approach which retains the simplicity and reliability of anther culture while eliminating the need for either mechanical disruption1,2 or surgical manipulation4 of anthers.

Unconventional methods in plant breeding.

There are three wass whereby unconventional methods of plant genetics can be used for applied plant breeding. 1. The time necessary for breeding by recombination can be shortened, making use of the discovery that plants can be obtained directly from the products of meiosis, the "Gonen." Two new cultivars bred in tobacco by this method already exist. 2. Microbiological methods may be applied to mutation and selection in haploid or dihaploid cell cultures. New cultivars bred by this method have not yet been published, but it should be possible to make use of this technique in plant breeding. 3. Somatic hybridization of plants by fusions of protoplasts or by uptake of nuclei and other organelles (plastids, mitochondria) or pure nucleic acids is another useful method. There exist up to now somatic hybrid plants (a) between mutants of the liverwort Sphaerocarpos donnellii, (b) some varieties of tobacco, and (c) two species of Nicotiana. All these hybrids can also be produced by conventional sexual hybridization. It is impossible to predict how often incompatibility for cross-fertilization can be surmounted by somatic hybridization, as incompatibility between two genomes must be restricted to the fertilization process, but it can work on any stage of the development of the hybrid.

Heterosis and the future of animal improvement.

HETEROSIS AND THE FUTURE OF ANIMAL IMPROVEMENT* I. MICHAEL LERNERf The target of this symposium is an important but ill-understood phenomenon, and the stated purpose for which we have been convened here is to review our current knowledge of it, to throw some light on its biological basis, and above all, to explore its potentialities for use in animal breeding. Heterosis is a subject which has been continuously discussed in the 20 or so years since the first major compilation of papers specifically devoted to it [1] appeared. In the last several volumes of Animal Breeding A bstracts, references on heterosis include a great number of review articles and books in many languages. Its molecular foundations , some of which have been anticipated by Haldane [2, 3], have recently been subjected to a thorough examination [4], Its application in plant and animal breeding has been widespread. Examples of its occurrence in natural populations and in domesticated species are numerous. Evidence for its existence predates by many decades or even centuries the invention of the term, and experimental investigations in a more or less methodical manner have been carried out on it for considerably more than half a century. And, of course, in its broad sense, heterosis was not unknown territory to Darwin and to generations of breeders before him. Yet it is fair to say that (1) there is no general agreement as to the precise meaning of the term, (2) there are many theories and ideas about the biological basis of heterosis but only a few hard facts, and (3) there is no proof that methods of animal improvement purporting * Presented at the Symposium on Heterosis held by the Polish Academy of Sciences in Warsaw, Poland, and arranged by the Institute of Genetics and Animal Breeding at Jastrzebiec, September 27-October 2, 1971. To be published in a Polish translation in the proceedings of the symposium. ? Department of Genetics and Institute for Personality Assessment and Research, University of California, Berkeley, California 94720. Perspectives in Biology and Medicine · Summer 1973 | 581 to utilize it are, indeed, optimal for all species in all situations. Even in corn production, where crosses between inbred lines are beginning to enjoy a worldwide monopoly, it has by no means been established unequivocally that breeding for heterotic performance is operationally the soundest procedure to follow. These are matters sufficiently well known not to require elaboration on my part. In any case, I shall assume that their features relevant to our collective task here will be covered by others with more competence and knowledge of biological and practical detail than I possess. Since I have no new experimental data, or any novel hypothesis to account for heterosis, or any fresh theoretical concepts to place before you, the question as to what I am doing here is obviously highly pertinent. Yet it is possible that I may have a minor contribution to make to this meeting. It will not be based on my previously published discussion of genetic homeostasis [5] to which I probably owe my presence here. Nor will it relate to my book on selection [6], which I am happy to note may be known not only to those of you at home with the English language but also to those who can read it with better comprehension than I can in its Polish translation. Rather, the gist of my remarks will be an extension of the considerations that governed Professor Hugh Donald and myself when we embarked on our attempt to discuss animal breeding in a broad social context [7]. Again, I am pleased to record that this work, true enough in a somewhat mutated form mostly as a result of deletions but in part because of changes in the course of transcription, is available in Russian, a language with which I together with others here can claim some familiarity. With this volume as a starting point, I want, by discussing some general problems and issues stemming from what may be flatteringly described as philosophical and social points of view, to provide a somewhat vaguely stated footnote to our proceedings here. Heterosis in Scientific Literature I do not feel compelled to survey the vast literature...

An examination of stimulatory effects of ionizing radiation in plants

Stimulatory effects of ionizing radiations were investigated with X-rays in seeds ( Helianthus, Fagopyrum), plants ( Fagopyrum) and leaf disks ( Nicotiana and Phaseolus). About 1,600 plants and over 400 leaf disks were employed and over 28,000 individual measurements were made. Small but significant growth increases were produced in certain instances but such results were not always reproducible from one experiment to another. Also, when increases did occur, they were not always produced by the same exposure levels. On the basis of these results—the great variability associated with the appearance of positive stimulatory effects and the relatively small increases that are produced—it is doubtful that ionizing radiations, except for genetic and plant-breeding applications, are likely to become useful in increasing agricultural crop yields on a commercial scale. Some of the data obtained in these experiments suggest that low exposures of radiation may result in depression of growth of dividing cells, but stimulation of growth of expanding cells.

Implications of Genotype‐Environmental Interactions in Applied Plant Breeding1

Implications of Genotype‐Environmental Interactions in Applied Plant Breeding¹

SELF-STERILITY, SELF-FERTILITY, INBREEDING--AND HETEROSIS: GENETICAL INTERPRETATION, AND APPLICATION IN PASTURE PLANT BREEDING

It is not the object of this paper to supply specific information on the behaviour of pasture plants under various conditions of fertilization. I shall at,tempt to review some of the results obtained in work on various organisms, in the search for those principles which are fundiental to the phenomena forming the subject of this paper; fundamentals which, I admit,.may -q. not generally allow of a direct application in economic plant breeding, but which may ,lead the way to new ideas and. to 'new methods of procedure.

Notes on the Tundra of Russian Lapland

HAVING been invited by Professor N. I. Vavilov, Director of the Bureau of Applied Botany and Plant Breeding in Leningrad, to visit the plant breeding stations of Russia, I availed myself of the opportunity in the summer of 1926. My observations on the vegetation in the far North were made incidentally during a short visit to the Plant Breeding Station at Khibiny, which is the most northerly plant breeding laboratory in the world. I left Leningrad, August 24th, 1926, and travelled north by train two days to Khibiny, past Lake Onega and the White Sea, into the Kola Peninsula, through a country of lakes, woods and swamps, which had been heavily glaciated, and was much like parts of northern Canada. Many plant species are the same as in Canada, and many of the common plants are rarities in the British flora, often found only in the Highlands of Scotland or in the north of England. Many of the species are circumpolar in high latitudes, and a large number bear the name of Linnaeus himself. The distance from Leningrad to Khibiny is nearly 1000 -miles. Dr Eichfeld, Director of the Plant Breeding Laboratory at Khibiny, came down to Leningrad to meet me and take me north. He was an Esthonian and spoke German fluently, so we had no language difficulty. He lives at the Khibiny Laboratory from April to November and spends the winter in Leningrad. The Laboratory is one of many in different parts of the vast Russian territory, controlled from the central Bureau in Leningrad. Fromthis Bureau varieties of agricultural plants are sent out for testing to all these stations, and many valuable comparative results are being accumulated. Their mention here is not out of place, because they have, particularly in this instance, an ecological as well as a genetical bearing; for the comparative effects of the great range of climates to be found within Russian territory upon a wide range of identical crop plants are being determined, and in the extreme conditions of the North these climatic effects are most marked. The site of the Laboratory seems to have been well chosen, since, while in the tundra, it is considerably sheltered by the surrounding mountains, being on the eastern side of Lake Ymandra. Nevertheless, the winds are exceedingly strong and penetrating, reminding one of a mid-Atlantic gale. Khibiny is north of the Arctic Circle, in lat. about 67? 44'. The station is chiefly devoted to the breeding of vegetables suitable for this northern climate. Many varieties of potatoes are being tested, also beets, sugar beets, radishes, and other